Cacaluta is a 1km-long slice of paradise that's protected by an island, backed by dunes and usually deliciously deserted. The Mexican road-trip movie Y T煤 Mam谩 Tambi茅n was famously filmed there. Swimming is possible, although there can be undertow. Snorkeling is best around the island. There are no services at the beach, so bring plenty of water. A paved road off Hwy 200 leads to a 2.5km trail to the beach.
Alternatively, you can reach the beach by motorboat (M$2000 per boat) departing from Santa Cruz harbor.